Many patients in the world suffer from renal failure from multiple underlying conditions including hypertension, genitourinary tract infections, and diabetes, a condition that affects about 20 million people in the United States alone.
Unfortunately, many of these renal failure patients result in progression to ESRD, which requires dialysis where the blood is filtered and when possible eventually a renal transplant. Dialysis options include temporary central catheter treatment, peritoneal dialysis and hemodialysis via fistulae or grafts placed in the arms connecting an artery and vein. The vein is accessed to allow blood to flow from the patient's vein to a dialysis machine, which has a filter that removes waste, surplus fluids, and balances electrolytes. The filtered blood is then returned to the patient's vein downstream from the arterial access site. Many patients and healthcare providers prefer hemodialysis via arms sites as the best hemodialysis option.
If the patient elects hemodialysis as a treatment option for the end stage renal disease, the following procedure is typical. The patient's arm veins are evaluated clinically and measured with duplex ultrasound to find a vein that is 3 mm or larger. A 3 mm vein is a suitable candidate for surgical connection to an artery. The patient's arm arteries are palpated for a pulse to find a target artery to which the vein is to be connected. The physician connects the target artery and vein either at the wrist or elbow depending on the best vein and its location. In this manner, the physician forms a fistula between the two vessels. In the example where the connection is made at the wrist, the fistula can be made between the radial artery and the cephalic vein at the wrist (brescia fistula). The patient is sent home with instructions to exercise his/her hand and arm during the day to increase blood flow in the artery and vein with the hope that this exercise will increase the vein size by the increased flow. One often used exercise technique involves squeezing a device such as a ball with the hope that the vein will enlarge. The patient is observed for about six to eight weeks to monitor if enlargement of the vein has occurred keeping in mind that at least a 10 mm diameter vein would provide for better quality dialysis as compared to a smaller vein diameter. If after weeks of such exercise, the vein does not enlarge or thrombose, alternative treatment options are discussed. Such alternative treatment options include another fistula placement in another location, fistula salvage by endovascular means, synthetic graft placement, or catheter placement.
Many studies have concluded that arm veins connected to arteries provide the most dependable, durable vascular access option for hemodialysis. After this procedure connecting the arm vein and artery, patients are told to wait and watch if their vein becomes large enough to be used for dialysis. It is hard to predict which veins will enlarge to the appropriate size for dialysis use. Unfortunately, many arm veins fail to dilate and enlarge enough after subjecting them to arterial flow to allow for dialysis to occur. Some patients are told that their veins are too small and others are given no justification. This results in more surgery and possible graft placement or prolonged catheter usage at higher costs to society. Each eventual procedure also has increased risks to the patient as dialysis is delayed.
In some cases where the vein is considered sufficiently large for hemodialysis, but below the 10 mm diameter target, it can be more susceptible to function loss in a relatively short period of time during the hemodialysis treatment. Fistulae last longer if the vessel used for dialysis is properly dilated to the target diameter of about 10 mm. The vein being treated undergoes significant trauma as a patient typically undergoes about three hemodialysis sessions per week. Eventually the fistula (vein) to which the artery is connected fails in that it does not stay dilated or functional. This failure can happen more quickly when the vein fails to dilate to the optimum diameter before hemodialysis. Once the vein fails, another vein and artery must be connected to provide another vein for hemodialysis. This process requires surgery and is uncomfortable and there are a limited number of veins that are suitable for dialysis.
Extensive research has shown that intermittent compression, external heat application, and topical agents like nitric oxide help dilate superficial veins. Typically, when a dialysis technician initiates dialysis treatment where a needle is place in the target vein, the technician will apply intermittent pressure on the patient's arm with their fingers to dilate the vein prior to needle placement.
There is a need to provide improved vein dilation methods and devices to sufficiently and/or effectively dilate a vein for hemodialysis or maintain vein dilation for a longer period, while a patient is undergoing hemodialysis treatment.